Process for treating steel and iron



Patented Oct. 31, 1933 PROCESS FOR TREATING STEEL AND IRON William H. Payne, Middletown, Ohio, assignor to The American Rolling Mill Company, Middletown, Ohio, a corporation of Ohio No Drawing. Application November 5, 1931 Serial No. 573,308

3 Claims. (Cl. 148-4) My invention relates to methods of treating steel and iron which has been open annealed, whereby the formation of etched spots and streaks upon pickling of the same is avoided.

In the production of steel and iron material which is annealed in an open furnace, usually being given a normalizing treatment therein, it has been found very difiicult to avoid a surface condition which results in forming etched spots and streaks in subsequent pickling. This surface condition results from breaks in the oxide coating on the normalized or open annealed product, which breaks are in spots or cracks or scratches in the oxide. When the pickling treatment is applied to the sheets, the acid attacks .the metal laid bare at the breaks in the scale even in the presence of an inhibitor, resulting in forming marks which are not possible to eradicate.

In an attempt to avoid marking sheets during normalizing, it has been the practice to carry the material through the furnace on waster sheets,'

but this is not economical. The use of waster sheets was introduced on the theory that breaks in the oxide scale and therefore markings on the 26 final sheets were due to mechanical handling.

As was stated above, the marking is due primarily to breaks in the scale formed in open annealing or normalizing, or its subsequent handling, and this is caused not only by mechanical equipment in the furnaces, but by numerous other contingencies. Where an excess of oxygen or carbon dioxide is present in the furnace, the oxide formed is heavy and when the product cools, this oxide will crack, forming hair lines and checked places of exposed metal. Oil or other substances on the sheet may cause gas to be entrapped during normalizing, thus raising scale blisters which burst on cooling, leaving bare metal exposed. Open annealed and normalized 40 sheets are sometimes wavy and when cooled and piled, the waves are flattened by the weight of superimposed sheets, and this causes a checking of the scale. bundle will be'likely to give a like result. In fact, any one of a large number of fairly unavoidable contingencies will cause scale breaks in open annealed and normalized products. Hence the use of waster sheets is not adequate to avoid etch.

spots and streaks.

According to my process, I do not direct my efforts to avoiding scale breaks in open annealed Bending of the sheets in a crane apparently eliminates the etching action altogether and results in an even unmarked pickled surface, without use. of waster sheets, efforts for extreme care for cleanliness of product, even atmosphere in furnaces, special crane or conveyor precaution, etc., which are a great expense and not completely eifective.

My preferred method of forming the new thin scale to cover the open anneal or normalizing scale, is to place the sheets in an annealing box and heat them up high enough to form the required new scale over the exposed lines or patches of the former scale. I find that if I heat a bundle of open annealed sheets long enough to bring the entire mass up to around 1200 degrees Fahrenheit, or'even as low as 1000 degrees Fahrenheit, which isby no means a box annealing treatment, and does not effect a grain structure change in the product, that the required scale will be formed over the bare metal lines and patches of the product. In some cases the eifect requires a holding of the sheets at the elevated temperature as in soaking.

Thistreatment requires a base, for best results a cover and a sand seal, together with a furnace large enough to hold the said equipment. There is no particularity in cooling and the cover can be removed from the annealing box when convenient, having regard for formation of a thin scale only,- which in some materials will require a delay until a lower temperature has been reached. There is no particularity as to time of heating except that the entire product be brought up to temperature. There is no particularity as to temperature except that it should be such aswill form a scale under annealing conditions. Of course, to give the product a full box annealing treatment would have the same effect, but this would be expensive andthe final product will no longer have the characteristics of an open annealed sheet.

I contemplate other ways of forming a thin scale, comparative to the scale which will be formed by the scale anneal treatment that I have. just described. The method described is merely the cheapest and quickest one that I have available, using regular steel mill equipment.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. The method of producing open annealed steel and iron sheets, which comprises first open annealing said sheets, second forming a thin scale over any exposed bare metal of the open annealed product prior to pickling by annealing said sheets at such low temperatures thatthe product is not deprived of its open led character= i'stics, and third, pickling said sheets.

2. The method of producing open annealed menace w pen annealed iron sheets, which comprises first open alone" i i I said sheets, second to a thin scale over any exposed bare metal of the open annealed product prior to pickling, by heating the said product under box annealing conditions sum- 3. The method of produc steel and cientonly to form said scale, said heating being such as'to bring all parts of the said product to around 1,000 F. as a and without depriving the product of its open ealed acteristics.

W In I MM H. IPA.

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